1. Field of the Invention
The present invention relates to a suspension structure for a power unit mounted in a rear part of an electric vehicle.
2. Description of Related Art
In recent years, electric vehicles (EVs) that run with a drive force of a motor (electric motor) have been provided along with vehicles having a gasoline engine in consideration of the global environment. A power unit including the motor and a motor speed reducer is mounted in a rear part of the electric vehicle.
Since such a power unit has a relatively large capacity and weight, a conventional electric vehicle includes a special structure with high rigidity in a lower part of a vehicle body, such as on a rear floor, to suspend the power unit (for example, see JP 4508260 B, JP 2008-222032 A, JP 2008-195259 A, and JP 2003-72392 A). As an example, a frame for suspending a power unit in a lower part of the vehicle body is provided around the power unit.
However, in the structure for suspending the power unit in the conventional electric vehicle described above, relative positions of the power unit, the frame, and the vehicle body, and a position of a suspension portion of the power unit from the vehicle body are not determined with sufficient consideration of loads generated in a vertical direction, a width direction, and a front-back direction of the vehicle when running, and a rotating load in the vertical direction of the vehicle due to torque variations of the motor during driving or deceleration. Thus, the loads cannot be efficiently absorbed, and propagation of vibrations to the vehicle body cannot be reduced.
In conventional suspension structures, when a front impact load or a rear impact load is applied to the vehicle, and the load cannot be efficiently absorbed, a rubber bush in the suspension portion of the power unit from the vehicle body may break, or the power unit may be brought into contact with a structure in a front part of the vehicle.
Furthermore, in conventional suspension structures, when a lateral impact load is applied to the vehicle, a structure in a side part of the vehicle is easily brought into contact with the power unit, and a high voltage cable of the motor and a motor electrode terminal may break.